The present invention relates to an indicator for ethylene oxide gas (hereinafter referred to as "EOG") which is used for sterilization of medical materials and the like.
EOG is extensively used in the sterilization of medical and pharmaceutical materials such as instruments and fabrics, and there has been an urgent demand for the development of a visual indicator for indicating whether or not sterilization by EOG has been completed. However, no satisfactory indicator for EOG has been found heretofore.
There are known various types of indicators for EOG including one which changes its color from yellow to blue when exposed to EOG. However, these known indicators are disadvantageous in that the difference between the colors before and after EOG sterilization is very slight and difficult to distinguish, the resulting color disappearing in a short time after the color change, or the indicators are so sensitive to EOG that a very small amount of EOG can cause a complete color change and it is therefore almost impossible to judge whether or not sufficient EOG sterilization has been effected. Thus, there has been a great need for an improved indicator which is effective for practical use.
The present invention has been developed as a result of our studies for overcoming the above mentioned drawbacks of the known indicators for EOG.